Apparatuses, systems and methods for detecting corona

ABSTRACT

Apparatuses, systems and methods for detecting corona using audio data are disclosed. A method of processing audio data to detect corona includes determining an indicator of energy at a substantially fundamental frequency in the audio data, determining an indicator of the energy at a plurality of harmonic frequencies in the audio data, determining an indicator of the noise energy in the audio data, determining a comparison indicator of the noise energy relative to the energy at the harmonic frequencies, determining a masking indicator having thresholds for each of the harmonics relative to the fundamental frequency, and determining a corona detection indicator. An apparatus for detecting corona includes a memory, an audio detector configured to obtain the audio data near an electrical conductor in an AC system, and a processor to process the audio data, fundamental and harmonic frequencies of the audio data and their corresponding thresholds to detect corona.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation patent application Ser. No.14/202,940, filed Mar. 10, 2014, which claims the benefit of U.S.provisional patent application Ser. No. 61/781,496, and is acontinuation in part of U.S. national phase application Ser. No.13/825,451 based on International Application PCT/US2011/001632, filedSep. 22, 2011, each of which is incorporated herein by reference in itsentirety.

FIELD OF THE INVENTION

The present application relates to the detection of corona using audiodata. Some illustrative embodiments of the present invention relate tothe detection of corona on power transmission lines using audio data.

BACKGROUND OF THE INVENTION

Power Grids

FIGS. 1-4 illustrate related art disclosed in U.S. Pat. No. 8,002,592.FIG. 1 shows a transmission tower 200 which is used to suspend powertransmission lines 202 above the ground. The tower 200 has cantileveredarms 204. Insulators 206 extend down from the arms 204. One or moresuspension clamps 208 are located at the bottom ends of the insulators206. The lines 202 are connected to the suspension clamps. The clamps208 hold the power transmission lines 202 onto the insulator 206.

FIGS. 2-4 illustrate an example of a suspension clamp 208, whichgenerally comprises an upper section 210 and a lower support section212. These two sections 210, 212 each contain a body 214, 216 which forma suspension case. The bodies 214, 216 each comprise a longitudinaltrough (or conductor receiving area) 215, 217 that allow thetransmission conductor 202 to be securely seated within the two sectionswhen the two sections are bolted (or fastened) together by threadedfasteners 201 (not shown). This encases the transmission conductor 202between the two bodies to securely contain the transmission conductor202 on the clamp 208. Threaded fasteners are not required and any othersuitable fastening configuration may be provided.

The two bodies 214, 216 connected together are suspended via a metalbracket 218 that attaches to the lower body 216 at points via bolthardware 220.

The lower body, or lower body section, 216 comprise a first end 219 anda second end 221. The conductor receiving area (or conductor contactsurface) 217 extends from the first end 219 to the second end 221 alonga top side of the lower body 216. The conductor receiving area,including longitudinal trough 217, forms a lower groove portion forcontacting a lower half of the conductor 202. A general groove shape isnot required, and any suitable configuration may be provided.

In one implementation, the upper and lower sections 210, 212 each haveembedded within their respective bodies 214, 216 one-half of a currenttransformer 222, 224 that is commonly referred to in the industry as asplit core current transformer. When these components 222, 224 arejoined, they form an electromagnetic circuit that allows, in someapplications, the sensing of current passing through the conductor 202.In one implementation, the current transformer is used for powersensing, data collection, data analysis and data formatting devices. Insome implementations the current transformer may be located outside ofthe clamp or similar device or, in some implementations, power may beprovided by another means.

The body 214 of the upper section 210 contains a first member 232 and asecond member 234 forming a cover plate. The first member 232 comprisesa first end 233, a second end 235, and a middle section 237 between thefirst end 233 and the second end 235. The conductor receiving area (orconductor contact surface) 215 extends from the first end 233 to thesecond end 235 along a bottom side of the first member 232. Theconductor receiving area 215 forms an upper groove portion forcontacting an upper half of the conductor 202. A general groove shape isnot required, and any suitable configuration may be provided. In oneimplementation, the first member 232 further comprises a recessed cavity226 at the middle section 237 that effectively contains an electroniccircuit 228. In this implementation, the electronic circuit 228 isdesigned to accept inputs from several sensing components. This cavity226 may be surrounded by a faraday cage 230 to effectively nullify theeffects of high voltage EMF influence from the conductor 202 on thecircuitry 228. The faraday cage may also surround the currenttransformer 222. The cover plate, or cover plate member, 234 can coverthe top opening to the cavity 226 to retain the electronic circuitinside the body, or upper body section, 214. The electronics may behoused in a metal or plastic container, surrounded by the noted faradaycage, and the entire assembly can be potted, such as with epoxy forexample.

The electronic circuit 228 can accept and quantify in a meaningfulmanner various inputs for monitoring various parameters of the conductor202 and the surrounding environment. The inputs can also be derived fromexternally mounted electronic referencing devices/components. The inputscan include, for example: Line Current reference (as derived from theCurrent transformer 222, 224 or other means); Barometric pressure andTemperature references—internal and ambient (as derived from internaland external thermocouples 236, 238 or other means); Vibrationreferences of the conductor (as derived from the accelerometer 240, suchas a 0.1-128 Hz sensor, for example, or other means); and Opticalreferences (as derived from the photo transistor 242 in a fiber optictube or other means). The optical reference portion may, for example,allow the clamp to look up and see flashes of light from corona if theinsulator starts to fail, or lightening indication storm activity,and/or tensile references (as derived from the tension strain device 244which may be included in certain implementations). The tensilereferences from the tensile indicators 244 may, for example, provideinformation indicating that ice is forming as the weight of theconductor increases due to ice build up.

Supervisory Control And Data Acquisition (SCADA) generally refers to anindustrial control system such as a computer system monitoring andcontrolling a process. Information derived by the electrical/electroniccircuitry can exit the circuit 228 via a non-conductive fiber opticcable 246 and be provided up and over to the transmission tower 200 andultimately at the base of the tower and fed into the user's SCADA systemto allow the end user to access and view electrical and environmentalconditions at that sight, or the information can be transmitted to aremote or central site. The suspension clamp or other sensing device maybe alternatively configured to wirelessly transmit information from theelectronic circuit 228 to a receiver system.

Problems Associated with Corona and Conventional Corona DetectionSystems

Corona is a type of electrical discharge which will corrode or eat awayat wire, insulators, and anything else in the vicinity. Conventionalmethods of corona detection involve ultraviolet and ultrasonicdetection. Both suffer from a high cost of implementation and variousdisadvantages. For example, power lines can generate corona that can beseen by using special cameras operating in the ultraviolet spectrum.However, such cameras are large and expensive. The cameras are generallysent to places where an insulator appears to be eaten away, but may notbe effective since corona can be intermittent and is affected by manyenvironmental conditions such as moisture and air pressure. Further,conventional ultraviolet detectors require a user to manually operate adevice and aim at an area suspected to contain corona. As such, thesedetectors are cumbersome and not autonomous. Furthermore, conventionalultrasonic detectors employ nondiscriminatory means of detecting corona,seeking any noise in a given ultrasonic frequency range. Thus, thesedetectors are often not sufficiently accurate.

Repair or Servicing a Transmission Line

Initially, one must locate where a power transmission line is broken.However, power transmission lines can run hundreds of miles betweensubstations, and the only information generally available is that onesubstation is supplying power and the next one is not receiving thesupplied power. Accessibility to power transmission lines may vary. Insome cases, the power transmission lines may be accessible by motorizedground vehicles. In other cases, lines may only be accessible byhelicopter, wherein a service technician must hang under the helicopterto service or repair a line. Such repairs or maintenance can be veryexpensive. Accordingly, preventative methods of detecting problems suchas corona are needed.

Conventional Communication Protocols

In order to retrieve information about the system, rapid and securecommunication is necessary. Radio communication via Ethernet is oneoption. However, organizing an Ethernet network requires the use ofdevices known as routers or switches. Each router or switch will look atan Ethernet packet of information and make note of the source addressand the destination address as the packet arrives at a port. If thedestination is known, the packet is forwarded to only one port which isknown to be connected to that destination device. If it is not a knownaddress, it is repeated to all ports except the port where it arrived.When the destination device responds, the source address will appear ina packet on a single port which permit the router or switch to learnwhere to send the next packet with that particular destination address.

There are specific protocols which optimize the route for delivering apacket and to remove the opportunity for a packet to become repeated ina loop in the network. Some of the more common protocols are SpanningTree Protocol and Rapid Spanning Tree Protocol. A popular radio protocolfor packet-based transmission is Zigbee which is described in standardIEEE 802.15.4, but it is only useful in networks in a small geographicarea.

There is a need for accurate, inexpensive, small and easy-to-implementsystems and methods for detecting corona. These may allow for fastanalysis of any actual or potential repair problems and poweroptimization capabilities along transmission lines, with lower costs ofrepair, better preventative maintenance, and faster restore times. Aneed also exists for a way of collecting and communicating data by awidespread installation of sensing devices such as corona sensors overlarge geographic areas (such as power line grids).

SUMMARY OF THE INVENTION

Illustrative embodiments of the present invention address at least theabove problems and/or disadvantages, and provide at least the advantagesdescribed below.

An illustrative method and system for detecting corona can be operableto obtaining audio data by a detector near an electrical conductor; andprocess the audio data using a fundamental frequency corresponding tothe AC power signal in the conductor and a selected number of harmonicfrequencies of the audio data by a processor to detect corona indicativeof a corona condition, wherein thresholds are designated for each of theharmonic frequencies relative to the fundamental frequency and need tobe met to detect a corona condition.

In accordance with one or more of the following aspects of theillustrative embodiments, or different combinations thereof, the methodand system for detecting corona can process the audio data by

determining a first indicator of the energy at a substantiallyfundamental frequency in the audio data from an audio detector deployedto detect corona generated by an alternating current (AC) system,

determining a second indicator of the energy at a plurality of harmonicfrequencies in the audio data,

determining a third indicator of noise energy in the audio data,

determining a normalized indicator of the energy at each of the harmonicfrequencies in the audio data by dividing the energy at each of theharmonic frequencies by the first indicator, and

detecting a corona event if:

-   -   the second indicator, which corresponds to the sum of the energy        at each of the harmonic frequencies, is greater than the third        indicator of the noise energy in the audio data; and    -   each normalized indicator of the energy at each of the harmonic        frequencies in the audio data is within a range of acceptable        levels.

With regard to the method and system for detecting corona thefundamental frequency of the audio data is within an frequency rangeaudible to human beings.

The method and system for detecting corona can also communicate an alerton corona event detection.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other illustrative features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of certain illustrative embodiments thereof when taken inconjunction with the accompanying drawings in which:

FIG. 1 is a perspective view of a transmission tower supportingtransmission lines connected via suspension clamps;

FIG. 2 is a perspective view of a suspension clamp;

FIG. 3 is a cross section view of the suspension clamp shown in FIG. 2;

FIG. 4 is a perspective view of a first member of the suspension clampshown in FIG. 2;

FIG. 5 illustrates a signal-to-noise-ratio versus frequency graph of thefrequency responses of an example set of narrowband bandpass filtersaccording to an illustrative embodiment of the present invention;

FIG. 6 illustrates a signal-to-noise-ratio versus frequency graph of anexample frequency mask for a corona detector according to anillustrative embodiment of the present invention;

FIG. 7a illustrates a block diagram of the operation of an example combfilter according to an illustrative embodiment of the present invention;

FIG. 7b illustrates a gain-to-frequency graph of the frequency responseof an example comb filter according to an illustrative embodiment of thepresent invention;

FIG. 8a illustrates an example process for detecting corona using audiodata according to an illustrative embodiment of the present invention;

FIG. 8b shows a block diagram of an illustrative apparatus for detectingcorona using audio data according to an illustrative embodiment of thepresent invention;

FIG. 9 illustrates a block diagram of an example of a method and asystem processing audio data to detect corona according to anillustrative embodiment of the present invention; and

FIGS. 10a-c show illustrative apparatuses for detecting corona usingaudio data according to illustrative embodiments of the presentinvention.

Throughout the drawings, like reference numerals will be understood torefer to like elements, features and structures.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

This description is provided to assist with a comprehensiveunderstanding of illustrative embodiments of the present inventiondescribed with reference to the accompanying drawing figures.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the illustrative embodimentsdescribed herein can be made without departing from the scope and spiritof the present invention. Also, descriptions of well-known functions andconstructions are omitted for clarity and conciseness. Likewise, certainnaming conventions, labels and terms as used in the context of thepresent disclosure are, as would be understood by skilled artisans,non-limiting and provided only for illustrative purposes to facilitateunderstanding of certain illustrative implementations of the embodimentsof the present invention.

Generally referring to FIGS. 5-9, various apparatuses, systems andmethods can detect or assist in the detection of corona according toillustrative embodiments of the present invention. For example, powerlines can generate corona that can sometimes be heard in the audiospectrum as a sizzling sound. Briefly, audio data can be collected onsite (e.g., a location or installation where corona may be present)using audio sensors in accordance with illustrative embodiments of thepresent invention. The audio data, including frequency properties of theaudio data (e.g., fundamental and harmonic frequencies) can be processedlocally and/or remotely with respect to the site. Corona can be detectedusing the sensed audio data and audio signatures of corona or thresholdcharacteristics, for example. If corona is detected, such detection canbe indicative of a corona condition of a conductor, and can bedocumented using time stamps, durations, and/or other parametersrelating to the detected corona event. For example, other parameters caninclude information about a level of corona detection, frequency ofcorona detection, or a percentage of time corona is detected over aselected period of time.

An audio spectrum is usually generated along with a corona in or nearhigh power environments, such as, for example, electrical power lines,step-down transformers, high power closets or substations or other powersources for cranes or industrial sites, and neon lamps. While such highpower environments are typically associated with voltages of about12,000 V or more, some illustrative embodiments of the present inventionmay be applicable to environments associated with any voltage level.

A corona discharge can be created in an alternating current (AC) systemat a voltage peak, that is, either at a positive voltage peak or at anegative voltage peak, but generally not both. Consequently, at most onedischarge generally occurs per AC cycle. The discharge generally doesnot persist as the voltage drops. The polarity of the dischargegenerally depends on the shape of an electrode from which coronaoriginates. Since at most one discharge usually occurs per AC cycle, anAC system generally creates an audio spectrum with a fundamentalfrequency equal to the frequency of the AC system. For example, a 60 HzAC system can create an audio spectrum with a fundamental frequency of60 Hz. It is however possible for corona to be discharged at bothpositive and negative voltage peaks. It is also possible that some ACcycles create audio spectra with fundamental frequency different fromthe frequency of the AC system. Accordingly, a fundamental frequency canbe arrived at or varied prior, during or after various elements,process(es) or modules employed by the methods or systems according tothe present invention. For example, stored corona detection data can beused to determine a desired fundamental frequency.

An audio spectrum can refer to a portion of the audible frequency rangeat which typical human beings can hear. This range can span, forexample, from 20 Hz to 20,000 Hz. An advantage of using audio data overultrasound data to detect corona is the superior affordability of audiodata detectors, such as conventional audio microphones and other audiodetectors, over ultrasound detectors.

Another advantage of using audio data over ultraviolet data to detectcorona can also be the smaller size, the ease of implementation and theautonomy of systems using conventional microphones and audio detectors,according to some illustrative embodiments of this invention, versusexpensive, large, non-autonomous ultraviolet cameras described above.

A further advantage of illustrative embodiments of the present inventiondisclosed herein is a higher accuracy in the audio spectrum detection ofcorona than conventional corona detection methods. While conventionalmethods, such as, for example, methods using ultrasound detection, donot discriminate among different inputs, some illustrative embodimentsdisclosed herein can seek particular frequency and amplitude patterns inprocessed audio data. Signal processing of audio data according toillustrative embodiments of the present invention, including, forexample, analysis of harmonic frequencies of audio data, results in moreaccurate detection of corona. As a result of this higher accuracy,corona detection can be more reliably implemented as a preventativemeasure for preserving the integrity of conductors such as powertransmission lines.

A further advantage of illustrative embodiments of the present inventiondisclosed herein is calibration of evaluation criteria. For example,based on historic data gathered using illustrative embodiments ofsystems and methods according to the present invention, frequencies orother parameters can be calibrated to provide more accurate coronadetection. Further, audio signatures of corona or thresholdcharacteristics can be provided or varied prior, during or after variouselements, process(es) or operation(s) or modules employed by theillustrative methods or systems according to the present invention.Stored corona detection data can be used to determine and then calibratedesired audio signatures of corona or threshold characteristics forcorona detection purposes (e.g., pre-calibrated data for deployment in acorona detection system).

As described below, illustrative methods or systems according to thepresent invention look for a specific pattern of harmonic peaks relativeto the fundamental in audio data to detect corona, and employ a mask forthe expected pattern and a range for the mask. An example frequency maskis described below with reference to FIGS. 6 and 9 (e.g., step 960).

FIG. 5 illustrates a signal-to-noise-ratio versus frequency graph 500 ofthe frequency responses of an example set of narrowband bandpassfilters. A series of evenly spaced narrow pulses with equalsignal-to-noise ratios, from an audio spectrum generated by an ACsystem, can produce a frequency spectrum with a spike at the fundamentalfrequency and spikes of equal signal-to-noise ratios at each harmonic.Similar spectra can be detected by applying a set of narrowband bandpassfilters with frequency responses as shown in FIG. 5. Digital signalprocessing can allow for the creation of accurate filters with bandsthat can be as narrow as required for a given application.

FIG. 6 illustrates a signal-to-noise-ratio versus frequency graph 600 ofan example frequency mask for a corona detector as employed inaccordance with illustrative embodiments of the present invention. Themask assumes the level of each harmonic is about the same, but thehigher harmonics are permitted to be more attenuated than the lowerorder harmonics. In other words, as the widths of pulses from an audiospectrum generated by an AC system increase, the signal-to-noise ratiosof the harmonics may decline at higher frequencies. The harmonics atlower frequencies may not be substantially affected by nominalvariations in the pulse width. Accordingly, example methods and systemsaccording to illustrative embodiments of the present invention use thefundamental and the next 11 harmonics. Other illustrativeimplementations of the present invention can use any number of harmonicsor frequency range of harmonic frequencies besides an illustrative rangeof 10-12 harmonics (i.e., that were selected in view of the dynamicrange of an illustrative 16-bit converter). While the range of harmonicsto be used can range from one to an upper range defined by a range of adetector, it may be preferable to use at least four harmonics. As statedabove, when using a mask (e.g., step 960), one may assume thesignal-to-noise ratios of the harmonics to be approximately uniform,although harmonics at higher frequencies can be more attenuated thanharmonics at lower frequencies without disturbing the process.Alternatively, a number of harmonics can be provided or varied prior,during or after various elements, process(es) or operation(s) or modulesemployed by the illustrative methods or systems according to the presentinvention. For example, stored corona detection data can be used todetermine and then designate a desired number of harmonics.

A spectrum having harmonics with energies essentially equal to theenergy between harmonics is generally insufficient to establish adetection of a corona event, because such a pattern can be produced bybackground or white noise. Rather, a spectrum having more energy inharmonics than energy between harmonics, or more energy than a multipleof the noise energy between harmonics, is generally a better indicatorof corona events. Thus, the illustrative methods or systems according topresent invention can use total energy between harmonics to determinecorona in the presence of noise and do not require determining energy inrespective harmonic frequencies or specific energy between two harmonicfrequencies to overcome the effects of noise when detecting corona. Thetotal noise energy between harmonics can be obtained, for example, witha comb filter, as illustrated in FIGS. 7a -b.

FIG. 7a illustrates a block diagram 700 of the operation of an examplecomb filter according to an illustrative embodiment of the presentinvention, and FIG. 7b illustrates a gain-to-frequency graph 750 of thefrequency response of an example comb filter according to anillustrative embodiment of the present invention. Any comb filter knownin the art can be implemented to determine the total noise energybetween harmonics in an audio spectrum generated by an AC system. Forexample, a feedforward notch filter can be implemented with a delayequal to a period of a fundamental frequency of the audio spectrum. Byway of example, an illustrative implementation can use a sample rate of8820 samples per second for a 60 Hz AC system and 7350 samples persecond for a 50 Hz AC system. This can result in a 147-sample delay foreither frequency. The input data can be subtracted from the delayeddata, resulting in a gain at the fundamental and each harmonic. The gaincan be 2 between harmonics.

In an example method, the total energy of the harmonics can be comparedto the total energy between the harmonics. An example algorithm (e.g.,employed by a processor 854) can require the harmonic energy to be atleast 4 times higher than the noise energy, such that the gain can beapproximately 6 dB. Alternative example algorithms can require theharmonic energy to be greater than any desired multiple of the noiseenergy. This amount of gain can be adequate to reliably detect mostsignificant corona.

FIG. 8a illustrates a block diagram 800 of a process according to anillustrative embodiment of the present invention for detecting coronausing audio data. Briefly, by way of an example, this illustrativemethod can include obtaining audio data (e.g., near an electricalconductor) at step 810, processing audio data using audio signatures orthreshold characteristics at step 820, and communicating an alert oncorona event detection at step 830.

FIG. 8b shows a block diagram of an illustrative apparatus 850 fordetecting corona using audio data according to an illustrativeembodiment of the present invention. Apparatus 850 can include audiodetector 852, processor 854, memory 856 and communication system 858.Audio detector 852, processor 854, memory 856 and communication system858 can be electrically or communicatively coupled, can be configured inthe same housing or be separate (e.g., the detector 852 and/or thecommunication system can be separate from the processor 854 and memory856), and can be configured to perform steps substantially similar toany of the steps in example method 800. Additional illustrativeembodiments of the present invention can include components that areenclosed or partially exposed, and can be located in or near a highpower environment, on or near a suspension clamp. The apparatus 850 canbe connected to a power source available at the site being monitored orcan comprise a battery.

At step 810, a detector 852 can obtain audio data, for example, near anelectrical conductor, which can be deployed over relatively largegeographic distances. The detector 852 can be located near, on or insidea clamp, in a closet, or anywhere with power conductor(s) or othercomponent(s) that are being monitored for corona. Audio data can beobtained using, for example, a microphone, or any other audio datadetector known in the art. For example, a conventional microphone can beused, which can be less costly than ultrasonic detectors required byconventional methods of detecting corona.

At step 820, the audio data can be processed using, for example, audiosignatures of corona or threshold characteristics. The audio data can beprocessed using, for example, a digital signal processor (DSP) or anyother processor 854 known in the art. The DSP or other processor 854 canbe local or remote. Audio signatures of corona or thresholdcharacteristics can be stored or determined, locally or remotely, usinga computer, machine-readable media, or other electronic circuitry.Alternatively, audio signatures of corona or threshold characteristicscan be provided or varied prior, during or after element(s), process(es)or operation(s) or modules employed by the illustrative methods orsystems according to the present invention. For example, stored orcollected corona detection data can be used to determine and thencalibrate desired audio signatures of corona or thresholdcharacteristics.

The output of the microphone 852 can be continually or periodicallysampled by the DSP or other processor 854. The sampled audio data can beprocessed using the DSP or other processor using audio signatures ofcorona or threshold characteristics.

At step 830, an alert signal or message can be communicated (e.g., bycommunication system 858) each time a corona event is detected, forexample, or after a particular number of detected corona events hasoccurred, for example, to assist with calibrating the DSP or otherprocessor 854 to more accurately characterize sounds as corona events.The DSP or other processor can then determine (e.g. using designatedaudio signatures of corona or threshold characteristics) whether analert should be generated indicating that a corona event has occurred.The alert signal or message can be communicated using any communicationmethod or systems known in the art, such as, for example, at least oneof wired or wireless communication, cell communication, Bluetooth®,ZigBee®, LAN, WLAN, RF, IR, or any other communication method or systemknown in the art. A communication can be in the form of at least one ofan email, a binary code, an e-mail message, an SMS message, a phonecommunication, a facsimile, or any other form of communication known inthe art. Each clamp in a power system can, for example, be configured tosend a message (e.g., a short e-mail message) to programmable e-mailaddresses in case of events such as current surges, excessive conductortemperature, excessive vibration, corona, and the like to ensure rapidand intelligent response to serious conditions. In an illustrativeembodiment of the present invention, a small message containing coronainformation can be sent, for example, using geographically distributedarrays over long distances. Radio protocols for very large networks canbe used to communicate alerts, for example, using methods and systemsdisclosed in commonly-owned International Application PCT/US2011/001632,filed Sep. 22, 2011. The collected and/or analyzed and/or reportedcorona event data can include, but is not limited to, time stamps,level, duration, periodicity/patterns, and correlation to coincidenttemperature, humidity and/or other conditions.

FIG. 9 is a block diagram of an example of a method and a system 900 forprocessing audio data to detect corona according to an illustrativeembodiment of the present invention. For example, block diagram 900shows an example of a system and method for performing step 820described above. An illustrative method and system 900 for processingaudio data can include such elements or modules as a bandpass filter901, a low-pass filter 902, a square root filter 903, a square filter904, a comb filter 905, a division 906, an adder 907, and a multiplier908. Briefly, in an illustrative implementation, a method and system 900for processing audio data to detect corona can include determiningbandwidth limited audio data at step 910, determining an indicator ofthe energy at a fundamental frequency at step 920, determining anindicator of the energy at each of a plurality of harmonic frequenciesat step 930, determining an indicator of the noise energy at step 940,determining a comparison indicator at step 950, determining an examplemask or masking indicator at step 960, and determining a coronadetection indicator at step 970. It will be understood by a personskilled in the art that some of these steps can be performed in anyorder.

In an illustrative method and system 900 for processing audio data todetect corona according to an illustrative embodiment of the presentinvention, a processor 854 with or without memory 856 can perform stepssubstantially similar to any of steps 910-970 using software, ordiscrete components (e.g., filters) can be used, or a combination ofboth. The system and method 900 for processing audio data to detectcorona according to illustrative embodiments the invention can beimplemented using software and/or hardware components.

In the illustrative implementations, at steps 920, 930 and 940, the rootmean square of the energy from each filter (e.g., respective bandpassfilters 910 in steps 920 and 930, and comb filter 905 in step 940) iscomputed by squaring the data 904, performing a low pass filter 902 toget an average, and then taking the square root 903. With regard tosteps 930 and 960, the results for each harmonic is then normalized tothe energy from the fundamental frequency using a division 906 as shownin step 960. The output of each divider 906 provides the energy in eachharmonic as a fraction of the energy in the fundamental frequency. Analternative implementation to using the root mean square function isdescribed below.

As stated above, audio data can include, for example, audio dataobtained from an audio detector (e.g., a microphone) deployed withrespect to an alternating current (AC) system. Audio data from the audiodetector can be analog-to-digital converted. In illustrativeimplementations, at step 910, bandwidth limited audio is provided to asystem 900 to reduce the processing requirements. The lower bandwidthsignal can be decimated (reduced sampling rate) before sampling. By wayof example, an illustrative implementation may reduce the sample ratefrom 44,100 samples per second to 8820 samples per second (⅕^(th) rate)for a 60 Hz AC system and 7350 samples per second (⅙^(th) rate) for a 50Hz AC system.

As explained above, the AC system will typically generate significantenergy at the fundamental frequency of the audio data and further energyat harmonics. For a power system, its fundamental frequency will usuallycontain the majority of the energy. As each frequency is analyzed, theroot mean square of the energy is computed. As described above, withreference to steps 920, 930 and 960, the energy at each harmonicfrequency separated by the bandpass filters is referenced to the energyat the fundamental frequency using a division 906 to normalize themeasured energy.

In illustrative implementations, at step 920, the energy of thefundamental frequency is measured and used as a normative reference forother measurements. The bandpass filter 901 isolates energy atfundamental frequency. In a typical AC power system, the fundamentalfrequency would be 60 Hz in the United States and other countries and 50Hz in Europe and other countries. The computation in step 920 (e.g. byprocessor 854) performs a root means square (rms) measurement. The datais squared, integrated, and a square root results in rms measurement.The low pass filter 902 in step 920 is, essentially, an integration. Theoutput of step 920 is the energy at the fundamental frequency. This isused as a reference. That is, the energy of the harmonics is computedrelative to the energy in the fundamental.

In illustrative implementations, at step 930, the energy at eachharmonic is computed using the root mean square. While the illustratedembodiment in FIG. 9 shows each bandpass filter is a multiple of 60 Hz,the implementation in a 50 Hz system would use bandpass filters whichare multiples of 50 Hz. The corner frequency of the 40 Hz low passfilters (e.g., integrators 901 in step 930) would change to 33.3 Hz fora 50 Hz system (i.e., 40 Hz*50/60=33.3 Hz). The output of eachharmonics' section within step 930 produces the rms energy at thatharmonic.

In illustrative implementations, at step 940, the energy between thebandpass filters implemented in steps 930 and 920 is measured. In thecase where the input signal is simply white noise, energy will bedetected in all of the bands, which might be erroneously considered apositive indication. By looking at energy between the harmonics, theillustrative implementation of the method and system 900 can determine anoise floor for the corona detection algorithm or system 900 (e.g.,performed by processor 854). The energy in the harmonics must besubstantially above the noise floor for the corona detection to becreated. The implementation uses, for example, a comb filter withnotches at the fundamental and all of the designated harmonics. The peakresponse of the comb filter will occur at (n+0.5)*fundamental frequency.For a 60 Hz fundamental, the peaks will be at 90 Hz, 150 Hz, 210 Hz, andso forth up to 750 Hz. Above 780 Hz there will be little energy due tothe 780 Hz bandpass filter in step 910.

In illustrative implementations, at step 950, a comparison indicator isgenerated. The indicators of the energy at each harmonic frequencydetected at step 930 are summed together in step 960 (e.g., using aprocessor 854 and a memory 856), and this total energy is compared with,for example, double the noise energy. If the sum of the indicators ofthe energy at each harmonic frequency is greater than the indicator oftwice the noise energy, a comparison indicator is set high. If not, thecomparison indicator 950 is set low. If the total energy from theharmonics exceeds twice the noise measured between the harmonics, thesignal may be considered for creation of a corona event (with furtherevaluation). If twice the noise energy exceeds the energy in theharmonics, the signal will be disqualified as corona.

In illustrative implementations, at step 960, a masking indicator can bedetermined. Normalized indicators of the energy at each harmonicfrequency can be determined by dividing each indicator of the energy ateach harmonic frequency by the indicator of the energy at thefundamental frequency. A mask can be applied to the normalizedindicators of the energy at each harmonic frequency, comparing eachnormalized indicator of the energy at each harmonic frequency with arange of acceptable levels. A range of acceptable levels can be uniformacross frequencies or can vary as a function of frequency. For example,a minimum value in a range of acceptable levels can range linearly ornonlinearly from about 15 dB for the lowest harmonic frequency to about5 dB for the highest harmonic frequency. Any other range of acceptablelevels can be used. Alternatively, a range of acceptable levels can beprovided or varied prior, during or after operation using methods orsystems according to the present invention. For example, stored coronadetection data can be used to determine and then calibrate a desiredrange of acceptable levels.

If all levels are within the mask, the masking indicator 960 can be sethigh. If not, the masking indicator can be set low. The maskingindicator 960 can be, for example, a mask block output.

In illustrative implementations, at step 970, a corona detectionindicator can be determined. A corona detection indicator 970 can be,for example, a corona detection bit, which can be output by an AND gate.If both the comparison indicator 950 and the masking indicator 960 arehigh, the AND gate output can be set high. If not, the AND gate outputcan be set low.

An alternative illustrative implementation can use absolute valuefunctions in place of square functions at steps 930 and 920. Thelow-pass filter may need a lower corner frequency, but the square rootat step 930 may not be needed. Even with such narrow filters, the outputmay not be a sine; consequently, the root mean square may be a moreaccurate method of measuring energy than the filtered absolute value,though the filtered absolute value may be good enough.

In an alternative illustrative method of processing audio data to detectcorona, at least some of steps 910-970 can be performed using aprocessor and a memory, without using some of blocks or modules 901-908illustrated in FIG. 9. Indicators in steps 910-970 can be variables.

FIGS. 10a-c show illustrative apparatuses 1000, 1020 and 1040 fordetecting corona using audio data according to illustrative embodimentsof the present invention, which can include processor 854 and audiodetector 852. Processor 854 and audio detector 852 can be electricallyor communicatively coupled, and can be configured to perform stepssubstantially similar to any of the steps in example method 800.

FIG. 10a shows an illustrative stand-alone apparatus 1010 for detectingcorona using audio data according to an illustrative embodiment of thepresent invention, which can include processor 854 having an integral orseparate memory 856 and audio detector 852.

FIG. 10b shows an illustrative apparatus 1020 for detecting corona usingaudio data according to an illustrative embodiment of the presentinvention, on a suspension clamp substantially similar to the suspensionclamp illustrated in FIGS. 2-4 described above. In illustrativeapparatus 1020, processor 854 and audio detector 852 can be electricallyor communicatively coupled to electronic circuit 228. In an alternativeillustrative embodiment of the present invention, electronic circuit 228can include a processor adapted to perform steps substantially similarto steps that processor 854 is adapted to perform.

FIG. 10c shows an illustrative apparatus 1040 for detecting corona usingaudio data according to an illustrative embodiment of the presentinvention, on a clamp assembly. The clamp assembly 1041 on a conductor1042 can include a clamp body 1043, a keeper body 1044 resting on theclamp body 1043, an electronics housing 1045, and a heat shield 1046that protects the electronic components in the electronics housing 1045.In illustrative apparatus 1040, processor 854 and audio detector 852 canbe electrically or communicatively coupled to an electronic circuitdisposed within electronics housing 1045.

The components of the illustrative devices, systems and methods employedin accordance with the illustrated embodiments of the present inventioncan be implemented, at least in part, in digital electronic circuitry,analog electronic circuitry, or in computer hardware, firmware,software, or in combinations of them. These components can beimplemented, for example, as a computer program product such as acomputer program, program code or computer instructions tangiblyembodied in an information carrier, or in a machine-readable storagedevice, for execution by, or to control the operation of, dataprocessing apparatus such as a programmable processor, a computer, ormultiple computers. Examples of the computer-readable recording mediuminclude, but are not limited to, read-only memory (ROM), random-accessmemory (RAM), CD-ROMs, magnetic tapes, floppy disks, optical datastorage devices. It is envisioned that aspects of the present inventioncan be embodied as carrier waves (such as data transmission through theInternet via wired or wireless transmission paths). A computer programcan be written in any form of programming language, including compiledor interpreted languages, and it can be deployed in any form, includingas a stand-alone program or as a module, component, subroutine, or otherunit suitable for use in a computing environment. A computer program canbe deployed to be executed on one computer or on multiple computers atone site or distributed across multiple sites and interconnected by acommunication network. The computer-readable recording medium can alsobe distributed over network-coupled computer systems so that thecomputer-readable code is stored and executed in a distributed fashion.Also, functional programs, codes, and code segments for accomplishingthe present invention can be easily construed as within the scope of theinvention by programmers skilled in the art to which the presentinvention pertains. Method steps associated with the illustrativeembodiments of the present invention can be performed by one or moreprogrammable processors executing a computer program, code orinstructions to perform functions (e.g., by operating on input dataand/or generating an output). Method steps can also be performed by, andapparatus of the invention can be implemented as, special purpose logiccircuitry, e.g., an FPGA (field programmable gate array) or an ASIC(application-specific integrated circuit).

Processors suitable for the execution of a computer program include, byway of example, both general and special purpose microprocessors, andany one or more processors of any kind of digital computer. Generally, aprocessor will receive instructions and data from a read-only memory ora random access memory or both. The essential elements of a computer area processor for executing instructions and one or more memory devicesfor storing instructions and data. Generally, a computer will alsoinclude, or be operatively coupled to receive data from or transfer datato, or both, one or more mass storage devices for storing data, e.g.,magnetic, magneto-optical disks, or optical disks. Information carrierssuitable for embodying computer program instructions and data includeall forms of non-volatile memory, including by way of example,semiconductor memory devices, e.g., EPROM, EEPROM, and flash memorydevices; magnetic disks, e.g., internal hard disks or removable disks;magneto-optical disks; and CD-ROM and DVD-ROM disks. The processor andthe memory can be supplemented by, or incorporated in special purposelogic circuitry.

The above-presented description and figures are intended by way ofexample only and are not intended to limit the present invention in anyway except as set forth in the following claims. It is particularlynoted that persons skilled in the art can readily combine the varioustechnical aspects of the various elements of the various exemplaryembodiments that have been described above in numerous other ways, allof which are considered to be within the scope of the invention.

The above-described illustrative embodiments of an apparatus, system andmethod can include program instructions, which can be stored onnon-transient computer-readable media to implement various operationsperformed by a processor, such as microprocessor or computer. The mediamay also include, alone or in combination with the program instructions,data files, data structures, and the like. The media and programinstructions may be those specially designed and constructed for thepurposes of the present invention, or they may be of the kind well-knownand available to those having skill in the computer software arts.Examples of computer-readable media include magnetic media such as harddisks, floppy disks, and magnetic tape; optical media such as CD ROMdisks and DVD; magneto-optical media such as optical disks; and hardwaredevices that are specially configured to store and perform programinstructions, such as read-only memory (ROM), random access memory(RAM), flash memory, and the like. The media may also be a transmissionmedium such as optical or metallic lines, wave guides, and so on, and isenvisioned include a carrier wave transmitting signals specifying theprogram instructions, data structures, and so on. The computer-readablerecording medium can also be distributed over network-coupled computersystems so that the computer-readable code is stored and executed in adistributed fashion. Examples of program instructions include bothmachine code, such as produced by a compiler, and files containinghigher level code that may be executed by the computer using aninterpreter. The described hardware devices may be configured to act asone or more software modules in order to perform the operations of theabove-described embodiments of the present invention.

Although illustrative embodiments of the present invention have beendisclosed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions, and substitutions arepossible, without departing from the scope of the present invention.Therefore, the present invention is not limited to the above-describedembodiments, but is defined by the following claims, along with theirfull scope of equivalents.

1. A method of processing audio data to detect corona comprising:obtaining audio data from an audio detector deployed to detect coronagenerated by an electrical component that is powered using alternatingcurrent (AC), the audio detector operated in the frequency range from 20Hertz (Hz) to 20,000 Hz, and the audio data having a substantiallyfundamental frequency corresponding to the AC; determining a totalenergy of harmonics in the audio data by summing the energy at each of aselected number of harmonic frequencies; determining a total noiseenergy between a selected number of harmonics in the audio data; andcomparing the total energy of the harmonics with the total noise energybetween a selected number of harmonics for corona detection.
 2. Themethod of claim 1, wherein the comparing comprises detecting coronausing a total energy corresponding to the total energy of harmonicsbeing a selected multiple times higher than the total noise energy. 3.The method of claim 1, further comprising disqualifying the audio datafor detecting corona if the total energy of harmonics does not exceed aselected multiple of the total noise energy.
 4. An apparatus fordetecting corona comprising: an audio detector operated in the frequencyrange from 20 Hertz (Hz) to 20,000 Hz, the audio sensor being deployedrelative to an electrical component powered using alternating current(AC) for detecting audio energy of corona and outputting correspondingaudio data, the audio data having a substantially fundamental frequencycorresponding to the AC; a processing device configured to receive theaudio data from the audio detector and to process the audio data bydetermining total energy of harmonics by summing the energy at each of aselected number of harmonic frequencies in the audio data; a filterconfigured to determine total noise energy between a selected number ofharmonics in the audio data; wherein the processing device is furtherconfigured to compare the total energy of harmonics with the total noiseenergy between a selected number of harmonics.
 5. The apparatus of claim4, wherein the processing device detects corona using a total energycorresponding to the total energy of harmonics being a selected multipletimes higher than the total noise energy.
 6. The apparatus of claim 4,wherein the processing devices disqualifies the audio data for coronadetection if the total energy of harmonics does not exceed a selectedmultiple of the total noise energy between a selected number ofharmonics.